The present invention relates to a digital communication system, a transmitter, and a data selecting apparatus and, more particularly to a digital communication system, a transmitter, and a data selecting apparatus, in which data is transmitted to many receiver groups for each receiver or for each receiving group comprising specified receivers.
In recent years, in many cases, video data, audio data or other data is transmitted or stored in the form of digital data. In such cases, these data is generally divided into data such as packets having a data structure comprising plural fields, to be transmitted or stored. Also, in some cases, plural pieces of data is made into a packet, and then packets are multiplexed to be transmitted through a transmission medium or to be stored in a storage medium. MPEG system standard is a standard for a data structure and multiplexing for this case, and data is transmitted or stored by a method according to a packet data structure according to this standard.
Conventionally, in a system in which such packet data is multiplexed, equipment which receives data is adapted to select data to-be-received from the multiplexed packet data. By way of example, a method for transmitting data to each receiver and selecting data in each receiver in digital broadcasting using a data multiplexing method according to MPEG system standard will now be briefly described in brief.
In digital broadcasting, when key information used for decrypting encrypted video or audio data or an electric mail is transmitted, it is sometimes necessary that data ((hereinafter referred to as xe2x80x9cEMMxe2x80x9d (Entitlement Management message) data) be transmitted to specified receivers individually. In this case, a data structure termed xe2x80x9csectionxe2x80x9d defined in MPEG system standard is employed. The section data used for transmitting the EMM data, comprises a field of xe2x80x9ctable identifierxe2x80x9d indicating that type of corresponding data is the EMM data, a field indicating the number of a destination receiver, and a field which contains data to-be-transmitted.
The receiver which receives such data is provided with a data selecting apparatus for selecting required data. The data selecting apparatus contains the table identifier indicating the EMM data and a receiver number inherent to the receiver.
When the receiver receives the section data, the table identifier is taken out of the received data to check whether this indicates the EMM data. When this indicates the EMM data, a field of the receiver number is taken out of the received data to check whether this matches the receiver number inherent to the receiver. When a match is found between them, the data selecting apparatus selects and outputs this section data, whereby only data for the receiver can be selected.
By the way, recently, in order to send a variety of information with flexibility and only to desired receivers, it is required that receivers be grouped and data be sent to each group besides sending information to receivers individually. It is also required that the same data be sent to all the receivers simultaneously. Further, it is necessary to select receivers being specially served under a receiving contract and send data only to these receivers simultaneously.
However, in the transmission method of the EMM data and the data selecting method according to a prior art, since the data to-be-transmitted has a structure in which the information indicating the EMM data is stored in the table identifier field, and the number of the destination receiver is stored in the receiver number field, at the receiver side, whenever the table identifier field indicates the EMM data, it is checked whether the value of the receiver number field matches the receiver number of itself, and only when there is a match between them, the EMM data is selected and received.
With a data structure in which a receiver has a receiver number uniquely determined for each receiver, data is sent to only one receiver specified by a transmission end, and it is therefore impossible to simultaneously send data to a receiver group comprising plural receivers or on a contract broadcasting service basis. Hence, when individual data is sent for the receiver group or on the broadcasting service basis, it is necessary to specify receivers one by one and sequentially send the data to them. So, one transmission end requires several hundreds thousand to several millions of receivers, and accordingly, the method in which the data is sequentially sent to the receivers specified one by one, requires enormous data transmission bandwidth for flexible data transmission to the receivers. With a restricted data transmission bandwidth for broadcasting, flexible data transmission adapted to various services or in response to users"" demands is not realized, and thereby quality of service is degraded.
In Japanese Published Patent Application (No. Hei. 7-143117), there is disclosed a communication terminal in which a service group number stored in a receiver which has a right to receive a program is compared to a service group number specified in transmitted program data and when a match is found between them, the program is received.
In this communication terminal, when information destined for an individual ID is received, detection of match of service type numbers is first conducted, and decision on match of the individual ID is then conducted, which increases the amount of processing required for deciding whether the information destined for the individual ID can be received.
The present invention is conceived in view of the background art, and an object of the present invention is to provide a digital communication system in which data is simultaneously sent to all receivers or a prescribed receiver group, as well as to specified receivers, and a transmitter and a data selecting apparatus used in this system.
According to one aspect of the present invention, there is provided a digital communication system comprising: a transmitter for sequentially transmitting predetermined format data; and a plurality of receivers each including a data selecting apparatus for selecting required data from received data group and outputting selected data, wherein the transmitter transmits data to the receivers in one of a first transmission mode in which group destination directing information indicating that the data is to be transmitted to a receiving group consisting of predetermined receivers of the plurality of receivers, group specifying information for specifying a receiving group of receiving groups to which the data is to be transmitted, and in-group identification information for identifying a receiver in an arbitrary receiving group to which the data is to be transmitted, are included in the data, a second transmission mode in which the group destination directing information and the group specifying information are included in the data, and a third transmission mode in which the group destination directing information is included in the data.
According to another embodiment of the present invention, in the digital communication system of the earlier embodiment, the transmitter includes data structuring means for structuring data to be transmitted, and the data selecting apparatus includes: parameter storage means for prestoring plural parameters which are to be compared to the group destination directing information, the in-group identification information, and the group specifying information; correspondence pattern detecting means for comparing the information stored in the data to the parameters, respectively, to detect correspondence patterns; and output means for selecting the required data according to the correspondence patterns detected by the correspondence pattern detecting means and outputting the selected data.
According to another embodiment of the present invention, in the digital communication system of the above embodiment, the group destination directing information includes a group destination number indicating that the data to be transmitted is destined for a group when the data to be transmitted is destined for the group, the group destination directing information includes a specified receiver destination number indicating that the data to be transmitted is destined for a specified receiver when the data to be transmitted is destined for the specified receiver, the parameter storage means prestores a first parameter to be compared to the group destination number, a second parameter to be compared to the specified receiver destination number and the in-group identification information, and a third parameter to be compared to the group specifying information, the correspondence pattern detecting means detects one of first and second correspondence patterns in such a way that the first correspondence pattern is detected when the specified receiver destination number and the in-group identification information match the second parameter and the group specifying information matches the third parameter in the first transmission mode, and the second correspondence pattern is detected when the group destination number matches the first parameter and the group specifying information matches the third parameter in the second transmission mode, and the output means selects the required data according to one of the first and second correspondence patterns and outputs the selected data.
According to another embodiment of the present invention, in the digital communication system of the above embodiment, the group destination directing information includes a number for specifying all receivers when the data to be transmitted is destined for the all receivers, the parameter storage means prestores a fourth parameter to be compared to the number for specifying all receivers, the correspondence pattern detecting means detects a third correspondence pattern when the number for specifying all receivers matches the fourth parameter in the third transmission mode, and the output means selects the required data according to the third correspondence pattern and outputs the selected data.
According to another embodiment of the present invention, in the digital communication system of the above embodiment, the group destination directing information includes a special group number when the data to be transmitted is destined for all receivers which belong to a special group, when the data to be transmitted is destined for all receivers which belong to the special group, the parameter storage means prestores a fourth parameter to be compared to the special group number, the correspondence pattern detecting means detects a fourth correspondence pattern when the special group number matches the fourth parameter in the third transmission mode, and the output means selects the required data according to the fourth correspondence pattern and outputs the selected data.
In the digital communication system so constructed, data can be transmitted to a specified receiver, a predetermined receiving group, all receivers, or all receivers which belong to a special group, and selection of data in the receiver is performed with a small-scale circuit.
According to another embodiment of the present invention, there is provided a transmitter which is used in a digital communication system wherein data is structured to be in a predetermined format and is transmitted to a plurality of receivers, including: data structuring means for structuring data to be transmitted in one of a first data transmission mode in which group destination directing information indicating that the data is to be transmitted to a receiving group consisting of predetermined receivers of the plurality of receivers, group specifying information for specifying a receiving group of receiving groups to which the data is to be transmitted, and in-group identification information for identifying a receiver in an arbitrary receiving group to which the data is to be transmitted, are included in the data, a second data transmission mode in which the group destination directing information and the group specifying information are included in the data, and a third data transmission mode in which the group destination directing information is included in the data.
According to another embodiment of the present invention, in the transmitter of the above embodiment the group destination directing information in the first transmission mode includes a specified receiver destination number indicating that the data to be transmitted is destined for a specified receiver when the data to be transmitted is destined for the specified receiver.
According to another embodiment of the present invention, in the transmitter of an above embodiment, the group destination directing information in the second transmission mode includes a group destination number indicating that the data to be transmitted is destined for a group, when the data to be transmitted is destined for the group.
According to another embodiment of the present invention, in the transmitter of an above embodiment, the group destination directing information in the third transmission mode includes a number for specifying all receivers indicating that the data to be transmitted is destined for all receivers, when the data to be transmitted is destined for the all receivers.
According to another embodiment of the present invention, in the transmitter of an above embodiment, the group destination directing information in the third transmission mode includes a special group number indicating that the data to be transmitted is destined for all receivers which belong to a special group, when the data to be transmitted is destined for the all receivers which belong to the special group.
According to another embodiment of the present invention, there is provided a data selecting apparatus built in a receiver in a digital communication system, which is supplied with predetermined format data as inputs and selects required data from input data group and outputs selected data, and the apparatus comprises: parameter storage means for prestoring plural parameters which are to be compared to group destination directing information in the data indicating that the data to be transmitted is destined for a receiving group consisting of predetermined receivers of the plurality of receivers, group specifying information in the data for specifying a receiving group of receiving groups to which the data is to be transmitted, and in-group identification information in the data for identifying a receiver in an arbitrary receiving group to which the data is to be transmitted; correspondence pattern detecting means for comparing the information stored in the data to the parameters, respectively, to detect correspondence patterns; and output means for selecting the required data according to the correspondence patterns detected by the correspondence pattern detecting means and outputting the selected data.
According to another embodiment of the present invention, in the data selecting apparatus of the above embodiment, the group destination directing information includes a group destination number indicating that the data to be transmitted is destined for a group when the data to be transmitted is destined for the group, the group destination directing information includes a specified receiver destination number indicating that the data to be transmitted is destined for a specified receiver when the data to be transmitted is destined for the specified receiver, the parameter storage means prestores a first parameter to be compared to the group destination number, a second parameter to be compared to the specified receiver destination number and the in-group identification information, and a third parameter to be compared to the group specifying information, the correspondence pattern detecting means detects one of first and second correspondence patterns in such a way that the first correspondence pattern is detected when the specified receiver destination number and the in-group identification information match the second parameter and the group specifying information matches the third parameter, and the second correspondence pattern is detected when the group destination number matches the first parameter and the group specifying information matches the third parameter, and the output means selects the required data according to one of the first and second correspondence patterns and outputs the selected data.
In the data selecting apparatus so constructed, in the specified receiver, predetermined receivers which belong to the specified receiving group, all receivers, or the receivers which belong to the special group, selection of the transmitted data can be performed. Simultaneously, selection of the data in the receiver is performed with a small-scale circuit.